Hydraulic lift systems are known in the art for lifting heavy objects into pickup trucks. The design of many of these allow loading large, heavy items, such as heavy equipment, motorcycles, tractors, ATV's and snowmobiles. These items typically weigh from 500 to 5,000 pounds. Hydraulic lift systems usually lift the items from ground level and into the truck.
Hydraulic systems known in the art typically have a single pivot arm with either a direct hydraulic cylinder attachment or attachment to other components forming a link to the cylinder.
The amount of weight that the system can accommodate is limited by the amount of weight that the pivoting arm can accommodate when the pivot arm is fully extended. At the point where the pivot arm is fully extended, the hydraulic cylinder cannot exert significant force.
Optimum load bearing capability of the pivot arm occurs when the pivot arm is substantially perpendicular to the axis of rotation (90 degrees). As the pivot arm raises or lowers and the angle differential from 90 degrees increases, the load bearing capability of the pivot arm decreases.
A lever, such as the pivot arm, makes work easier by reducing the force needed to move a load. Work, in physics, is the product of the force used to lift a load multiplied by the distance the force, or effort, is applied. This relationship can be written mathematically as:Work=Force×Distance.
A leveraged hydraulic lift system depends on the placement of the fulcrum along the lever, the length of the force application side of the lever to relative to the length of the weight bearing side of the lever. The force application side of the lever must be as long as possible, and the weight bearing side of the lever must be as short as possible.
This presents a problem known in the art with respect to hydraulic lift systems for trucks. The truck bed length practically limits the length of the force application side of the lever. The length of the weight bearing side of the lever must be sufficient to contact an item on the ground and raise the item high enough to allow it to be stored. This can result in the weight bearing side of the lever becoming unwieldy and impractically long for lifting heavy objects.
Hydraulic lift systems known in art are limited as to the amount of weight they can lift by the length of the weight bearing side of the lever required for object clearance. Components such as tailgates and trailer hitches must often be removed from the rear of the truck to maximize leverage.